From 6777d773a463ac045d333b989d4e44660f8d92ad Mon Sep 17 00:00:00 2001 From: Mimi Zohar Date: Fri, 21 Aug 2009 14:32:48 -0400 Subject: kernel_read: redefine offset type vfs_read() offset is defined as loff_t, but kernel_read() offset is only defined as unsigned long. Redefine kernel_read() offset as loff_t. Cc: stable@kernel.org Signed-off-by: Mimi Zohar Signed-off-by: James Morris --- fs/exec.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/exec.c') diff --git a/fs/exec.c b/fs/exec.c index 4a8849e45b2..fb4f3cdda78 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -678,8 +678,8 @@ exit: } EXPORT_SYMBOL(open_exec); -int kernel_read(struct file *file, unsigned long offset, - char *addr, unsigned long count) +int kernel_read(struct file *file, loff_t offset, + char *addr, unsigned long count) { mm_segment_t old_fs; loff_t pos = offset; -- cgit v1.2.3 From a2a8474c3fff88d8dd52d05cb450563fb26fd26c Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Sat, 5 Sep 2009 11:17:13 -0700 Subject: exec: do not sleep in TASK_TRACED under ->cred_guard_mutex Tom Horsley reports that his debugger hangs when it tries to read /proc/pid_of_tracee/maps, this happens since "mm_for_maps: take ->cred_guard_mutex to fix the race with exec" 04b836cbf19e885f8366bccb2e4b0474346c02d commit in 2.6.31. But the root of the problem lies in the fact that do_execve() path calls tracehook_report_exec() which can stop if the tracer sets PT_TRACE_EXEC. The tracee must not sleep in TASK_TRACED holding this mutex. Even if we remove ->cred_guard_mutex from mm_for_maps() and proc_pid_attr_write(), another task doing PTRACE_ATTACH should not hang until it is killed or the tracee resumes. With this patch do_execve() does not use ->cred_guard_mutex directly and we do not hold it throughout, instead: - introduce prepare_bprm_creds() helper, it locks the mutex and calls prepare_exec_creds() to initialize bprm->cred. - install_exec_creds() drops the mutex after commit_creds(), and thus before tracehook_report_exec()->ptrace_stop(). or, if exec fails, free_bprm() drops this mutex when bprm->cred != NULL which indicates install_exec_creds() was not called. Reported-by: Tom Horsley Signed-off-by: Oleg Nesterov Acked-by: David Howells Cc: Roland McGrath Cc: James Morris Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/exec.c | 63 ++++++++++++++++++++++++++++++++++++++------------------------- 1 file changed, 38 insertions(+), 25 deletions(-) (limited to 'fs/exec.c') diff --git a/fs/exec.c b/fs/exec.c index fb4f3cdda78..172ceb6edde 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1015,6 +1015,35 @@ out: EXPORT_SYMBOL(flush_old_exec); +/* + * Prepare credentials and lock ->cred_guard_mutex. + * install_exec_creds() commits the new creds and drops the lock. + * Or, if exec fails before, free_bprm() should release ->cred and + * and unlock. + */ +int prepare_bprm_creds(struct linux_binprm *bprm) +{ + if (mutex_lock_interruptible(¤t->cred_guard_mutex)) + return -ERESTARTNOINTR; + + bprm->cred = prepare_exec_creds(); + if (likely(bprm->cred)) + return 0; + + mutex_unlock(¤t->cred_guard_mutex); + return -ENOMEM; +} + +void free_bprm(struct linux_binprm *bprm) +{ + free_arg_pages(bprm); + if (bprm->cred) { + mutex_unlock(¤t->cred_guard_mutex); + abort_creds(bprm->cred); + } + kfree(bprm); +} + /* * install the new credentials for this executable */ @@ -1024,12 +1053,13 @@ void install_exec_creds(struct linux_binprm *bprm) commit_creds(bprm->cred); bprm->cred = NULL; - - /* cred_guard_mutex must be held at least to this point to prevent + /* + * cred_guard_mutex must be held at least to this point to prevent * ptrace_attach() from altering our determination of the task's - * credentials; any time after this it may be unlocked */ - + * credentials; any time after this it may be unlocked. + */ security_bprm_committed_creds(bprm); + mutex_unlock(¤t->cred_guard_mutex); } EXPORT_SYMBOL(install_exec_creds); @@ -1246,14 +1276,6 @@ int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs) EXPORT_SYMBOL(search_binary_handler); -void free_bprm(struct linux_binprm *bprm) -{ - free_arg_pages(bprm); - if (bprm->cred) - abort_creds(bprm->cred); - kfree(bprm); -} - /* * sys_execve() executes a new program. */ @@ -1277,20 +1299,15 @@ int do_execve(char * filename, if (!bprm) goto out_files; - retval = -ERESTARTNOINTR; - if (mutex_lock_interruptible(¤t->cred_guard_mutex)) + retval = prepare_bprm_creds(bprm); + if (retval) goto out_free; - current->in_execve = 1; - - retval = -ENOMEM; - bprm->cred = prepare_exec_creds(); - if (!bprm->cred) - goto out_unlock; retval = check_unsafe_exec(bprm); if (retval < 0) - goto out_unlock; + goto out_free; clear_in_exec = retval; + current->in_execve = 1; file = open_exec(filename); retval = PTR_ERR(file); @@ -1340,7 +1357,6 @@ int do_execve(char * filename, /* execve succeeded */ current->fs->in_exec = 0; current->in_execve = 0; - mutex_unlock(¤t->cred_guard_mutex); acct_update_integrals(current); free_bprm(bprm); if (displaced) @@ -1360,10 +1376,7 @@ out_file: out_unmark: if (clear_in_exec) current->fs->in_exec = 0; - -out_unlock: current->in_execve = 0; - mutex_unlock(¤t->cred_guard_mutex); out_free: free_bprm(bprm); -- cgit v1.2.3